The present invention disclosed herein relates to a laser device, and more particularly, to a multiple distributed Bragg reflector type laser device.
Semiconductor-based optical devices may be manufactured through a variety of semiconductor processes such as a growth process, a photolithography process, an etching process, a deposition process, and/or the like. By using the semiconductor processes, the semiconductor-based optical devices can be reduced in their sizes, costs and/or mass-produced. Accordingly, many researches on the semiconductor-based optical devices have been progressed.
Among the semiconductor-based optical devices, functional laser devices for selecting specific wavelengths, such as a distributed feedback laser diodes and/or distributed Bragg reflector type laser diodes, have been developed. The functional laser devices can perform wavelength filtering using diffraction gratings. For example, a light wave having a specific wavelength corresponding to a Bragg wavelength can be reflected. That is, the wavelength filtering is realized. The reflected light wave having the specific wavelength is oscillated by feedback to a gain region. The functional laser devices may be used as not only light sources for communication but also light sources for generating terahertz (Thz) waves by for example photo-mixing.
A frequency doubling method, a backward wave oscillator, a photo-mixing method, a carbon dioxide pumping gas laser, a quantum cascade laser, a free electron laser, and the like are used for generating the terahertz waves. In the photo-mixing method, beating signals of two different laser beams are incident on the photo-mixer to attain a terahertz wave corresponding to a beating cycle. For the photo-mixing method, a frequency of at least one of the two different laser beams should be stably continuously tuned. In addition, properties of the two different laser beams should be harmonized with each other. In order to meet these requirements, additional devices are further required and thus an apparatus for performing the photo-mixing method for generating the terahertz waves is large-sized and complicated. In addition, the cost for the apparatus increases.